Electronic devices such as personal computers and mobile terminals include universal serial bus (USB) ports. Such type of an electronic device incorporates, for example, a rechargeable battery and a charge circuit for charging the rechargeable battery. The charge circuit charges the rechargeable battery with power supplied through the USB port from a USB host.
Various types of power supply ports, which supply charging power, are specified as the USB ports of the USB host. For example, three types of power supply ports, namely, a standard downstream port (SDP), a charging downstream port (CDP), and a dedicated charging port (DCP), are defined by the USB battery charging standard, which has been formed as an extended version of the USB specification.
The SDP, which is the same port as that defined in the USB 2.0 specification, is typically included in a USB host and a USB hub. The SDP is capable of supplying current of 0.5[A] at most to an electronic device (USB device). The CDP is defined as a port capable of performing charging with a larger current than the SDP while maintaining a USB communication function in the USB host or the USB hub. The CDP is capable of supplying current of 1.5[A] at most to the USB device. The SDP and the CDP each use two data terminals D+, D− of the USB port to perform enumeration (connection recognition) through data communication between the USB device and the USB host.
The DCP is defined as a port dedicated to charging and does not have the USB communication function. Thus, the DCP is arranged in a power supply device (USB host) such as an AC adapter or a car adapter, which does not perform the enumeration. The DCP is capable of supplying current of 1.5[A] at most to the USB device.
The electronic device (USB device) detects the electrical state of the two data terminals D+, D− of a USB port to identify the type of the USB host connected to the USB port. For example, when the two data terminals D+, D− are short-circuited, the USB host is identified as the DCP (i.e., USB host including DCP).
Japanese Laid-Open Patent Publication Nos. 2011-234355 and 2010-171589 describe the above related art.